drm/i915: Remove dead scaler register defines

We have some duplicated scaler register defines that are
never used. Remove them.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230426135019.7603-3-ville.syrjala@linux.intel.com